Atlanta - World of Coca Cola
**Edit: It would be about an hour out of the way from Atl, but if you can fit it in (so to speak) the Stone Mountain Laser Show is definitely worth it.
Arizona - Arizona Meteor Crater, Flagstaff/Sedona (GREAT driving roads, and scenery)
**Edit x2: When driving from Vegas to Grand Canyon/Flagstaff, most likely will be driving down 93. Straight, flat 2 lane state highway, very minimally patrolled outside of towns. Good spot to "open her up" a little.